You are new to Iyengar yoga, you get to class, and the teacher says “roll your arms out.” A typical response would be “my arms don’t roll anywhere because they are attached to my torso.” At least that is what I thought when I first heard the nebulous instruction. After years of classes, it finally hit me what the instructor meant. Hopefully this post will save you a few years.
First of all, think of a cross section of your humerus bone in the upper arm or your femur bone in the thigh as the axle of a wheel. The direction to “roll in” means that the flesh and muscle move from the outward to the inward. The direction “roll out” means the flesh and muscle move from the inward to the outward.
A clearer illustration is that of an old time towel wringer that you find at do-it-yourself car washes.
Think of your thighs as the two cylinders of this contraption. When the “thighs roll in” the towel moves backwards. When the “thighs roll out” the towel moves forward.
To now practically illustrate this point. Use a block between the thighs for Tadasana.
To “roll the thighs in” the block will eject backwards. To”roll the thighs out” the block will move forward. It is not recommended to roll the thighs out in Tadasana as it will put strain on your back.
What happens to the rest of the body when the thighs roll in during Tadasana? These are the types of questions you should ask yourself during home practice to build knowledge. The first thing that happens is that your sacrum spreads and the tailbone moves forward. When the sacrum spreads and the tailbone moves forward the chest lifts. When the chest lifts the arms roll out (from inner to outer). When the arms roll out the chest spreads. When the chest spreads the trapezium softens away from the neck. When the trapezium softens away from the neck the head floats on the spine and there is no pressure in your shoulders.
So like a game of Mousetrap, each movement effects the next movement and the next ad nauseam.
In the Iyengar system, these movements go from the gross to the subtle and from the physical to the consciousness. So next time you practice on your own, ask yourself which movement effects what other part of your body, and then trace that movement until you have exhausted all the options. You will find it is never ending.